Osmotic and ionic regulation

Process ichnology and the elucidation of physico-chemical stress

Various functional group hypotheses have provided different prehctions for the influence of mobile deposit feeders on the composition of marine soft-sediment communities. Two that have received particular attenhon are the trophic group amensalism and mobhty mode hypotheses. Trophic group amensalism suggests that deposit feeders will primarily affect suspension feeders through resuspension of sediments while a rnobhty mode approach suggests that sediment disruption is the mechanism of interaction, with sedentary organisms being the group most adversely affected. The macrofauna around a dense intertidal bed of the burrowing ghost shnmp Callianassa californiensis (Dana) was studied to test the predictions of these hypotheses. Most sedentary species, including deposit feeders, had much lower numbers withm a dense shrimp bed compared to adjacent areas of low C. cahforniensis numbers. However, there was no change in fauna1 richness. These distributions are consistent with a mobihty mode of interaction and are in contrast with recent studies of the ghost shrimp's effect on subtidal bivalve populations.

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Changes in a benthic community associated with dense beds of a burrowing deposit feeder, Callianassa californiensis

7 – Oxygen Transport in the Blood

1. The respiratory responses of two mud-shrimps, Callianassa californiensis and Upogebia pugettensis (Thalassinidea), from Yaquina Bay, Newport, Oregon, were measured.2. Both species are metabolic regulators, showing oxygen-independent respiration above the critical oxygen tension for C. californiensis of 10-20 mm Hg (6.- 12.5% air-saturation) and for U. pugettensis of 45-50 mm Hg (28-31% air-saturation).3. Within the independent range of respiration, C. californiensis has a mean metabolic rate of 0.029 ml O2 x g wet wt-1 x hr-1, which is significantly lower than that of U. pugettensis (0.059 ml O2 x g wet wt-1 x hr-1).4. Heart rates of C. californiensis subjected to diminishing oxygen tensions show a regulatory pattern similar to the metabolic rate, with bradycardia occurring at ca. 27 mm Hg.5. Both species are tolerant to anoxia. C. californiensis survives approximately 5.7 days and U. pugettensis 3.3 days under such conditions.6. Preliminary data suggest that postmolt U. pugettensis do not regulate and...

Respiratory adaptations of two burrowing crustaceans, callianassa californiensis and upogebia pugettensis (decapoda, thalassinidea)

1 Callianassa californiensis and Upogebia pugettensis (Crustacea: Thalassinidea) have been studied with respect to their osmoregulatory capacities and selected aspects of their natural history Upogebia affinis and Callianassa filholi have been studied with respect to their osmoregulatory capacities2 Upogebia pugettensis has a discrete, open and durable burrow system and is distributed further up the Yaquina estuary than is C californiensis, which is without such a burrow system3 Resident species of thalassinids are exposed to brackish conditions in the winter and spring at Yaquina Bay4 The lower lethal salinity limit for U pugettensis and U affinis is approximately 10% SW; that for C californiensis is 25%-30% SW; that for C filholi is probably 35%-40% SW5 U pugettensis and U affinis are strong hyper-osmotic regulators below 75% SW In full strength SW, U pugettensis and U affinis are iso-osmotic, and the former species conforms osmotically in 125% SW In U pugettensis the ions of Na+, 

Lawrence C. Thompson

Papers

Osmoregulatory capacities of callianassa and upogebia (crustacea: thalassinidea)